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<h1 id="firstHeading" class="firstHeading">Dynamic exception specification <span class="t-mark-rev t-until-cxx17">(until C++17)</span></h1>
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<tr class="t-nv-h1"><td colspan="5"> Utilities</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="attributes.html" title="cpp/language/attributes"> Attributes</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Types</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="typedef.html" title="cpp/language/typedef"> <code>typedef</code> declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="type_alias.html" title="cpp/language/type alias"> Type alias declaration</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Casts</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="implicit_cast.html" title="cpp/language/implicit conversion"> Implicit conversions</a> - <a href="explicit_cast.html" title="cpp/language/explicit cast"> Explicit conversions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static_cast.html" title="cpp/language/static cast"><tt>static_cast</tt></a> - <a href="dynamic_cast.html" title="cpp/language/dynamic cast"><tt>dynamic_cast</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="const_cast.html" title="cpp/language/const cast"><tt>const_cast</tt></a> - <a href="reinterpret_cast.html" title="cpp/language/reinterpret cast"><tt>reinterpret_cast</tt></a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Memory allocation</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="new.html" title="cpp/language/new"> <code>new</code> expression</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="delete.html" title="cpp/language/delete"> <code>delete</code> expression</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> <a href="classes.html" title="cpp/language/classes"> Classes</a></td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class.html" title="cpp/language/class"> Class declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="initializer_list.html" title="cpp/language/constructor"> Constructors</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="this.html" title="cpp/language/this"> <code>this</code> pointer</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="access.html" title="cpp/language/access"> Access specifiers</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="friend.html" title="cpp/language/friend"> <code>friend</code> specifier</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Class-specific function properties</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="virtual.html" title="cpp/language/virtual"> Virtual function</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="override.html" title="cpp/language/override"> <code>override</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="final.html" title="cpp/language/final"> <code>final</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="explicit.html" title="cpp/language/explicit"><tt>explicit</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static.html" title="cpp/language/static"><tt>static</tt></a> </td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Special member functions</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="default_constructor.html" title="cpp/language/default constructor"> Default constructor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="copy_constructor.html" title="cpp/language/copy constructor"> Copy constructor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="move_constructor.html" title="cpp/language/move constructor"> Move constructor</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="as_operator.html" title="cpp/language/as operator" class="mw-redirect"> Copy assignment</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="move_operator.html" title="cpp/language/move operator" class="mw-redirect"> Move assignment</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="destructor.html" title="cpp/language/destructor"> Destructor</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"><a href="templates.html" title="cpp/language/templates"> Templates</a> </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class_template.html" title="cpp/language/class template"> Class template </a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function_template.html" title="cpp/language/function template"> Function template </a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="template_specialization.html" title="cpp/language/template specialization"> Template specialization</a></td></tr>   
<tr class="t-nv"><td colspan="5"> <a href="parameter_pack.html" title="cpp/language/parameter pack"> Parameter packs</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Miscellaneous </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="asm.html" title="cpp/language/asm"> Inline assembly</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="history.html" title="cpp/language/history"> History of C++</a></td></tr>
</table></div></td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="exceptions.html" title="cpp/language/exceptions"> Exceptions</a><div class="t-navbar-menu"><div><div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="throw.html" title="cpp/language/throw"> throw-expression</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function-try-block.html" title="cpp/language/function-try-block"> function-try-block</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="try_catch.html" title="cpp/language/try catch"> try/catch block</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="noexcept_spec.html" title="cpp/language/noexcept spec"> <code>noexcept</code> specifier</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="noexcept.html" title="cpp/language/noexcept"> <code>noexcept</code> operator</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink"> Dynamic exception specification</strong><span class="t-mark-rev t-until-cxx17">(until C++17)</span></td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p>Lists the exceptions that a function might directly or indirectly throw.
</p>
<h3><span class="mw-headline" id="Syntax">Syntax</span></h3>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>throw(</b></code><span class="t-spar">type-id-list</span><span class="t-mark">(optional)</span><code><b>)</b></code>
</td>
<td> (1)
</td>
<td> <span class="t-mark-rev t-deprecated-cxx11">(deprecated in C++11)</span><br><span class="t-mark-rev t-until-cxx17">(removed in C++17)</span>
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<div class="t-li1"><span class="t-li">1)</span> Explicit dynamic exception specification</div>
<table class="t-par-begin">


<tr class="t-par">
<td> <span class="t-spar">type-id-list</span>
</td>
<td> -
</td>
<td> comma-separated list of <a href="type-id.html#Type_naming" title="cpp/language/type">type-ids</a><span class="t-rev-inl t-since-cxx11"><span>, a type-id representing a <a href="parameter_pack.html#Pack_expansion" title="cpp/language/parameter pack">pack expansion</a> is followed by an ellipsis (...)</span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>
</td></tr></table>
<p>An explicit dynamic exception specification shall appear only on a function declarator for a function type, pointer to function type, reference to function type, or pointer to member function type that is the top-level type of a declaration or definition, or on such a type appearing as a parameter or return type in a function declarator.
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw4">void</span> f<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span>            <span class="co1">// OK: function declaration</span>
<span class="kw4">void</span> <span class="br0">(</span><span class="sy2">*</span>pf<span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span> <span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span>       <span class="co1">// OK: pointer to function declaration</span>
<span class="kw4">void</span> g<span class="br0">(</span><span class="kw4">void</span> pfa<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>  <span class="co1">// OK: pointer to function parameter declaration</span>
<span class="kw1">typedef</span> <span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span>pf<span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// Error: typedef declaration</span></pre></div></div>
<h3><span class="mw-headline" id="Explanation">Explanation</span></h3>
<p>If a function is declared with type <code>T</code> listed in its dynamic exception specification, the function may throw exceptions of that type or a type derived from it.
</p><p><a href="incomplete_type.html" title="cpp/language/incomplete type" class="mw-redirect">Incomplete types</a>, pointers or references to incomplete types other than cv <code>void*</code><span class="t-rev-inl t-since-cxx11"><span>, and rvalue reference types</span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span> are not allowed in the exception specification. Array and function types, if used, are adjusted to corresponding pointer types, top level cv-qualifications are also dropped. <span class="t-rev-inl t-since-cxx11"><span><a href="parameter_pack.html" title="cpp/language/parameter pack">parameter packs</a> are allowed</span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>.
</p><p>A dynamic exception specification whose set of adjusted types is empty <span class="t-rev-inl t-since-cxx11"><span>(after any packs are expanded)</span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span> is non-throwing. A function with a non-throwing dynamic exception specification does not allow any exceptions.
</p><p>A dynamic exception specification is not considered part of a function’s type.
</p><p>If the function throws an exception of the type not listed in its exception specification, the function <span class="t-lc"><a href="../error/unexpected.html" title="cpp/error/unexpected">std::unexpected</a></span> is called. The default function calls <span class="t-lc"><a href="../error/terminate.html" title="cpp/error/terminate">std::terminate</a></span>, but it may be replaced by a user-provided function (via <span class="t-lc"><a href="../error/exception/set_unexpected.html" title="cpp/error/set unexpected">std::set_unexpected</a></span>) which may call <span class="t-lc"><a href="../error/terminate.html" title="cpp/error/terminate">std::terminate</a></span> or throw an exception. If the exception thrown from <span class="t-lc"><a href="../error/unexpected.html" title="cpp/error/unexpected">std::unexpected</a></span> is accepted by the exception specification, stack unwinding continues as usual. If it isn't, but <span class="t-lc"><a href="../error/bad_exception.html" title="cpp/error/bad exception">std::bad_exception</a></span> is allowed by the exception specification, <span class="t-lc"><a href="../error/bad_exception.html" title="cpp/error/bad exception">std::bad_exception</a></span> is thrown. Otherwise, <span class="t-lc"><a href="../error/terminate.html" title="cpp/error/terminate">std::terminate</a></span> is called.
</p>
<h3><span class="mw-headline" id="Potential_exceptions">Potential exceptions</span></h3>
<p>Each function <code>f</code>, pointer to function <code>pf</code>, and pointer to member function <code>pmf</code> has a <i>set of potential exceptions</i>, which consists of types that might be thrown. Set of all types indicates that any exception may be thrown. This set is defined as follows:
</p>
<div class="t-li1"><span class="t-li">1)</span> If the declaration of <code>f</code>, <code>pf</code>, or <code>pmf</code> uses a dynamic exception specification<span class="t-rev-inl t-until-cxx11"><span> that does not allow all exceptions</span> <span><span class="t-mark-rev t-until-cxx11">(until C++11)</span></span></span>, the set consists of the types listed in that specification.</div>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<div class="t-li1"><span class="t-li">2)</span> Otherwise, if the declaration of <code>f</code>, <code>pf</code>, or <code>pmf</code> uses <a href="noexcept.html" title="cpp/language/noexcept"><code>noexcept(true)</code></a>, the set is empty.
</div></td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<div class="t-li1"><span class="t-li">3)</span> Otherwise, the set is the set of all types.</div>
<p>Note: for implicitly-declared special member functions (constructors, assignment operators, and destructors)<span class="t-rev-inl t-since-cxx11"><span> and for the inheriting constructors</span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>, the set of potential exceptions is a combination of the sets of the potential exceptions of everything they would call: constructors/assignment operators/destructors of non-variant non-static data members, direct bases, and, where appropriate, virtual bases (including default argument expressions, as always)
</p><p>Each expression <code>e</code> has a <i>set of potential exceptions</i>. The set is empty if <code>e</code> is a <a href="constant_expression.html" title="cpp/language/constant expression">core constant expression</a>, otherwise, it is the union of the sets of potential exceptions of all immediate subexpressions of <code>e</code> (including <a href="default_arguments.html" title="cpp/language/default arguments">default argument expressions</a>), combined with another set that depends on the form of <code>e</code>, as follows:
</p>
<div class="t-li1"><span class="t-li">1)</span> If <code>e</code> is a function call expression, let <code>g</code> denote the function, function pointer, or pointer to member function that is that is called, then
<dl><dd><ul><li> if the declaration of <code>g</code> uses a dynamic exception specification, the set of potential exceptions of <code>g</code> is added to the set;
</li></ul>
</dd></dl>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<dl><dd><ul><li> if the declaration of <code>g</code> uses <a href="noexcept.html" title="cpp/language/noexcept"><code>noexcept(true)</code></a>, the set is empty;
</li></ul>
</dd></dl>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<dl><dd><ul><li> otherwise, the set is the set of all types.</li></ul></dd></dl></div>


<div class="t-li1"><span class="t-li">2)</span> If <code>e</code> calls a function implicitly (it's an operator expression and the operator is overloaded, it is a <a href="new.html" title="cpp/language/new">new-expression</a> and the allocation function is overloaded, or it is a full expression and the destructor of a temporary is called), then the set is the set of that function.</div>
<div class="t-li1"><span class="t-li">3)</span> If <code>e</code> is a <a href="throw.html" title="cpp/language/throw">throw-expression</a>, the set is the exception that would be initialized by its operand, or the set of all types for the re-throwing throw-expression (with no operand).</div>
<div class="t-li1"><span class="t-li">4)</span> If <code>e</code> is a <a href="dynamic_cast.html" title="cpp/language/dynamic cast"><code>dynamic_cast</code></a> to a reference to a polymorphic type, the set consists of <span class="t-lc"><a href="../types/bad_cast.html" title="cpp/types/bad cast">std::bad_cast</a></span>.</div>
<div class="t-li1"><span class="t-li">5)</span> If <code>e</code> is a <a href="typeid.html" title="cpp/language/typeid"><code>typeid</code></a> applied to a dereferenced pointer to a polymorphic type, the set consists of <span class="t-lc"><a href="../types/bad_typeid.html" title="cpp/types/bad typeid">std::bad_typeid</a></span>.</div>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<div class="t-li1"><span class="t-li">6)</span> If <code>e</code> is a <a href="new.html" title="cpp/language/new">new-expression</a> with a non-constant array size, and the selected allocation function has a non-empty set of potential exceptions, the set consists of <span class="t-lc"><a href="../memory/new/bad_array_new_length.html" title="cpp/memory/new/bad array new length">std::bad_array_new_length</a></span>.
</div></td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw4">void</span> f<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// f()'s set is "int"</span>
<span class="kw4">void</span> g<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>            <span class="co1">// g()'s set is the set of all types</span>
 
<span class="kw1">struct</span> A <span class="br0">{</span> A<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>                  <span class="co1">// "new A"'s set is the set of all types</span>
<span class="kw1">struct</span> B <span class="br0">{</span> B<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>         <span class="co1">// "B()"'s set is empty</span>
<span class="kw1">struct</span> D<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> D<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span> <span class="br0">(</span><span class="kw4">double</span><span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span> <span class="co1">// new D's set is the set of all types</span></pre></div></div>
<p>All implicitly-declared member functions <span class="t-rev-inl t-since-cxx11"><span>and inheriting constructors </span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>have exception specifications, selected as follows:
</p>
<ul><li> If the set of potential exceptions is the set of all types, the implicit exception specification <span class="t-rev-inl t-until-cxx11"><span>allows all exceptions (the exception specification is considered present, even though it is inexpressible in code and behaves as if there is no exception specification)</span> <span><span class="t-mark-rev t-until-cxx11">(until C++11)</span></span></span><span class="t-rev-inl t-since-cxx11"><span>is <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span><span class="br0">(</span><span class="kw2">false</span><span class="br0">)</span></span></span></span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>.
</li><li> Otherwise, If the set of potential exceptions is not empty, the implicit exception specification lists every type from the set.
</li><li> Otherwise, the implicit exception specification is <span class="t-rev-inl t-until-cxx11"><span><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">throw</span><span class="br0">(</span><span class="br0">)</span></span></span></span> <span><span class="t-mark-rev t-until-cxx11">(until C++11)</span></span></span><span class="t-rev-inl t-since-cxx11"><span><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span><span class="br0">(</span><span class="kw2">true</span><span class="br0">)</span></span></span></span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>.
</li></ul>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">struct</span> A
<span class="br0">{</span>
    A<span class="br0">(</span><span class="kw4">int</span> <span class="sy1">=</span> <span class="br0">(</span>A<span class="br0">(</span><span class="nu0">5</span><span class="br0">)</span>, <span class="nu0">0</span><span class="br0">)</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    A<span class="br0">(</span><span class="kw4">const</span> A<span class="sy3">&amp;</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
    A<span class="br0">(</span>A<span class="sy3">&amp;&amp;</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
    ~A<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span>X<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw1">struct</span> B
<span class="br0">{</span>
    B<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
    B<span class="br0">(</span><span class="kw4">const</span> B<span class="sy3">&amp;</span><span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span> <span class="co1">// exception specification is "noexcept(true)"</span>
    B<span class="br0">(</span>B<span class="sy3">&amp;&amp;</span>, <span class="kw4">int</span> <span class="sy1">=</span> <span class="br0">(</span><span class="kw1">throw</span> Y<span class="br0">(</span><span class="br0">)</span>, <span class="nu0">0</span><span class="br0">)</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
    ~B<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span>Y<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw4">int</span> n <span class="sy1">=</span> <span class="nu0">7</span><span class="sy4">;</span>
<span class="kw1">struct</span> D <span class="sy4">:</span> <span class="kw1">public</span> A, <span class="kw1">public</span> B
<span class="br0">{</span>
    <span class="kw4">int</span> <span class="sy2">*</span> p <span class="sy1">=</span> new <span class="br0">(</span><a href="../memory/new/nothrow.html"><span class="kw700">std::<span class="me2">nothrow</span></span></a><span class="br0">)</span> <span class="kw4">int</span><span class="br0">[</span>n<span class="br0">]</span><span class="sy4">;</span>
    <span class="co1">// D has the following implicitly-declared members:</span>
    <span class="co1">// D::D() throw(X, std::bad_array_new_length);</span>
    <span class="co1">// D::D(const D&amp;) noexcept(true);</span>
    <span class="co1">// D::D(D&amp;&amp;) throw(Y);</span>
    <span class="co1">// D::~D() throw(X, Y);</span>
<span class="br0">}</span><span class="sy4">;</span></pre></div></div>
<h3><span class="mw-headline" id="Example">Example</span></h3>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;exception&gt;</span>
<span class="co2">#include &lt;cstdlib&gt;</span>
 
static_assert<span class="br0">(</span>__cplusplus <span class="sy1">&lt;</span> <span class="nu0">201700</span>, 
    <span class="st0">"ISO C++17 does not allow dynamic exception specifications."</span><span class="br0">)</span><span class="sy4">;</span>
 
<span class="kw1">class</span> X <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">class</span> Y <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">class</span> Z <span class="sy4">:</span> <span class="kw1">public</span> X <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">class</span> W <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw4">void</span> f<span class="br0">(</span><span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span>X, Y<span class="br0">)</span> 
<span class="br0">{</span>
    <span class="kw4">int</span> n <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
    <span class="kw1">if</span> <span class="br0">(</span>n<span class="br0">)</span> <span class="kw1">throw</span> X<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK</span>
    <span class="kw1">if</span> <span class="br0">(</span>n<span class="br0">)</span> <span class="kw1">throw</span> Z<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// also OK</span>
    <span class="kw1">throw</span> W<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// will call std::unexpected()</span>
<span class="br0">}</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <a href="../error/set_unexpected.html"><span class="kw792">std::<span class="me2">set_unexpected</span></span></a><span class="br0">(</span><span class="br0">[</span><span class="br0">]</span>
    <span class="br0">{</span>
        <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"That was unexpected!"</span> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/endl.html"><span class="kw1795">std::<span class="me2">endl</span></span></a><span class="sy4">;</span> <span class="co1">// flush needed</span>
        <a href="../utility/program/abort.html"><span class="kw967">std::<span class="me2">abort</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
    <span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
    f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">That was unexpected!</pre></div></div> 
</div>
<h3><span class="mw-headline" id="Defect_reports">Defect reports</span></h3>
<p>The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
</p>
<table class="dsctable" style="font-size:0.8em">
<tr>
<th> DR
</th>
<th> Applied to
</th>
<th> Behavior as published
</th>
<th> Correct behavior
</th></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/25.html">CWG 25</a>
</td>
<td> C++98
</td>
<td> the behavior of assignment and initialization<br>between pointers to members with different<br>exception specifications was unspecified
</td>
<td> apply the restriction<br>for function pointers<br>and references
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/973.html">CWG 973</a>
</td>
<td> C++98
</td>
<td> exception specification may contain functions types, but the<br>corresponding function pointer conversion was not specified
</td>
<td> specified
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/1267.html">CWG 1267</a>
</td>
<td> C++11
</td>
<td> rvalue reference types were allowed in exception specifications
</td>
<td> not allowed
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/1351.html">CWG 1351</a>
</td>
<td> C++98<br>C++11
</td>
<td> default argument (C++98) and default member initializer<br>(C++11) were ignored in implicit exception specification
</td>
<td> made considered
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/1777.html">CWG 1777</a>
</td>
<td> C++11
</td>
<td> <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">throw</span><span class="br0">(</span>T...<span class="br0">)</span></span></span> was not a non-throwing<br>specification even if <span class="t-c"><span class="mw-geshi cpp source-cpp">T</span></span> is an empty pack
</td>
<td> it is non-throwing<br>if the pack is empty
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/2191.html">CWG 2191</a>
</td>
<td> C++98
</td>
<td> the set of potential exceptions of a <code>typeid</code> expression<br>might contain <code>bad_typeid</code> even if it cannot be thrown
</td>
<td> contains <code>bad_typeid</code><br>only if it can be thrown
</td></tr></table>
<h3><span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <a href="noexcept_spec.html" title="cpp/language/noexcept spec"> <code>noexcept</code> specifier</a><span class="t-mark-rev t-since-cxx11">(C++11)</span>
</td>
<td>  specifies whether a function could throw exceptions</td></tr>
</table>

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